On Tue, Nov 22, 2022 at 12:57:15PM +0100, Jan Kara wrote:
> On Mon 21-11-22 10:15:58, Jeremi Piotrowski wrote:
> > On Mon, Nov 21, 2022 at 04:00:18PM +0100, Jan Kara wrote:
> > > 
> > > OK, attached patch fixes the deadlock for me. Can you test whether it fixes
> > > the problem for you as well? Thanks!
> > 
> > I'll test the fix tomorrow, but I've noticed it doesn't apply cleanly to
> > 5.15.78, which seems to be missing:
> > 
> > - 5fc4cbd9fde5d4630494fd6ffc884148fb618087 mbcache: Avoid nesting of cache->c_list_lock under bit locks
> >   (this one is marked for stable but not in 5.15?)
> > - 307af6c879377c1c63e71cbdd978201f9c7ee8df mbcache: automatically delete entries from cache on freeing
> >   (this one is not marked for stable)
> > 
> > So either a special backport is needed or these two would need to be applied as
> > well.
> 
> Right. The fix is against current mainline kernel. Stable tree backports
> are a second step once the fix is confirmed to work :). Let me know in case
> you need help with porting to the kernel version you need for testing.
> 

I confirm that this patch fixes things with the more complicated reproducer :)
Attached is my tweaked version of the patch that applies against 5.15.